Feta is a European PDO product which can only be manufactured in Greece. It’s primarily made from sheep milk or mixes with the goat milk. Normally in the traditionally made cow milk cheeses like — mozzarella or parmesan, they would extract the animal rennet from the male calf’s stomach.
Likewise for the traditional feta cheese, the rennet is obtained from an unweaned lamb stomach. That’s because of these enzymes can only be found in the unweaned lamb stomach with good efficiency. The efficiency will drop drastically once they start eating solid food.
And unfortunately, extraction of rennet involved the killing of the animal.
Is it possible to have feta without rennet? Yes, it’s possible with a substitution. That said, rennet contains some key enzymes which break down part of the milk protein, and kickoff the curd formation. These enzymes include chymosin and lipase.
For effective substitution, you can use the chymosin powder like this one for the curd formation. Many of these enzymes are extracted from the microbes. Yeast, in this case. So, you don’t have to worry about the heart-breaking animal affair.
Rennet used in cheese market today
For that reason, there was limited availability of animal rennet in the industry for years. Throughout time, people sought after effective rennets in place of animal rennet. Other than the chymosin powder, two examples of non-animal rennet are the vegetable rennet and microbial rennet.
Vegetable rennet is obtained from the plant’s extracts which showed coagulating properties. However, there is a grey zone where many of the so-called vegetable/vegetarian rennet also made from the extraction of fungus, namely Rhizomucor miehei.
In comparison, microbial rennet is much cheaper to get and widely available year-round. Therefore, most of the cheese factory today, including feta cheese, are mainly using the microbial rennet. If you use microbial rennet, one thing to note is the cheese aging should not be longer than 3-6 months, let alone year-long agings.
Read: Parmesan vs Gorgonzola.
The purpose of rennet in Feta cheese
Regardless of the type of rennet, the main purpose of rennet is to allow for milk protein (casein) to settle down and form curds. In the molecular level, rennet contains chymosin and other enzymes which acts like a pair of scissors to cut off the peptide tail (Casein-MicroPeptides) from the surface of casein micelles.
After the tails are removed, the caseins will now be able to bind to each other to form a huge mass of curd. In the case of sheep milk, the solid content is 2-3 times more than the cow’s goat milk. For example, in 1 gallon of cow or goat milk, you will normally get ~1 pound of cheese; But in 1 gallon of sheep milk, you will probably have 2-3 pounds of cheese.
You can learn more about the process here in my other article (with picture).
Are there any rennet-free feta cheese brands?
Most of the feta cheese in the US store does not contain animal rennet. For
Normally, they have stated to use “enzymes” or “culture” on the ingredient label. The “culture” means mesophilic or thermophilic bacteria. While the enzymes — chymosin is one of them — are usually extracted from the popular strain of fungus commonly used in the food industry.